The present invention relates to an apparatus and method for producing charcoal, and in particular an apparatus and method that utilizes an airless kiln composed of a composite layer of clay, dirt and sand, and a sawdust layer.
Charcoal is a dark, brittle substance that is used in color pigments, in drawing instruments, in gunpowder, and in odor, color and flavor filters. The most well known use of charcoal is as a fuel for cooking, particularly home barbecue cooking, in a briquette form. Small portions of charcoal burn well and make a suitable fuel.
Charcoal is composed primarily of ash and amorphous carbon, the latter comprising carbon made of small irregularly arranged particles of graphite, which is a pure form of carbon.
Charcoal also includes trace amounts of impurities, such as hydrogen compounds and sulfur. Charcoal is produced by heating plant or animal material rich in carbon, such as wood, bones or other vegetation, in kilns that contain little or no air. The material in the kiln is combusted, and during heating, a majority of the oxygen, hydrogen and nitrogen escapes from the burning materials. The remaining product is a dark, porous material, which is charcoal.
Wood charcoal is one of the most common types of charcoal, and consists primarily of carbon, with traces of ash and other impurities. Activated charcoal is charcoal from which the impurities have been removed. Activated charcoal is normally produced by treating ordinary charcoal with steam and air heated to over 600° F. (315° C.).
Charcoal producing retorts, or kilns, are of varied types and structure. By way of example, workable kilns can be made of a mixture of dirt and cow manure. These kilns did not adequately isolate the interior of the kiln from air, and led to the possibility of emitting noxious, if not toxic, gasses as the temperature of the manure rose upon combustion of the wood inside the kiln.
Typical presently available charcoal-producing kilns and processes are disclosed in the prior art. For example, U.S. Pat. No. 1,538,505 disclose a process for providing charcoal in any type of retort, where the mineral matter from which the charcoal is produced is pre-treated to remove soluble inorganic matter before subjecting the mineral matter to a carbonizing process. U.S. Pat. No. 4,510,021 discloses a fluidized bed charcoal production system, utilizing a pyrolytic heating vessel, not an earth-sawdust combustion air-tight kiln. U.S. Pat. No. 4,583,992 discloses an upright, cylindrical down-draft gasifier having a rotatable grate. This patent does not disclose an air-tight kiln comprising walls of clay dirt and sawdust, as does the present invention. U.S. Pat. No. 4,856,491 disclose a solid fuel heating apparatus having primary and secondary combustion chambers, which is not air-tight, and emits a small amount of polluting particles. U.S. Pat. Nos. 5,435,983 and 5,551,958 each disclose charcoal-producing reactors that are partially insulated, and are made of metal material. Neither of these two latter references teach or disclose a kiln for producing charcoal comprising a combination of clay dirt and sawdust.